Physical aggression between intimate partners is harmful to individuals, families, and society, and thus there is substantial need for effective programs to prevent partner aggression from occurring or escalating. Motivational interviewing, a brief non-confrontational intervention designed to increase motivation to reduce harmful behavior, may be a valuable instrument to prevent partner aggression in young adults. The purpose of the proposed study is to conduct the first trial of motivational interviewing as a targeted prevention for partner aggression, using a sample of unmarried college student couples reporting low levels of male-to-female physical aggression. The goals are 1) to evaluate motivational interviewing as a method to prevent or reduce physical and psychological aggression, 2) to investigate the link between aggression reduction and improved well-being for the partner and relationship, and 3) to understand the mechanisms of change that lead to reductions in aggression following the intervention. Based on the transtheoretical model of change, I hypothesize that reductions in aggression will be mediated by greater motivation to change aggressive behavior, greater awareness of normative relationship behavior, and decreased acceptance of aggression.